Wikipedia:Reference desk/Archives/Science/2009 August 18

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August 18

Harvestman

What can I feed a harvestman? Mac Davis (talk) 00:13, 18 August 2009 (UTC)

Have you read the article? I found plenty of relevant information at Harvestman#Behavior. Intelligentsium 00:33, 18 August 2009 (UTC)

Small insects and "all kinds of plant matter"? I was looking for something specific. Maybe they are just not very picky. Thanks! Mac Davis (talk) 01:01, 18 August 2009 (UTC)

In her book Broadsides from the Other Orders, Sue Hubbell describes capturing some of them and keeping them for observation (including breeding). Apparently the most critical thing for their survival is a supply of fresh water, which they need constantly. This she supplied in a "shallow jar cap" set into the sand and dead leaves with which she covered the bottom of their wire-mesh cage. Other than that, "they lived in apparent contentment … until the end of their lives, thriving on a diet of overripe persimmons, cornmeal, bacon fat, and an occasional dead fly." The whole of Chapter 4 may be of interest if you can dig up a copy of the book. Deor (talk) 02:57, 18 August 2009 (UTC)

The book seems to be widely available in libraries. -Arch dude (talk) 07:11, 18 August 2009 (UTC)

I've struck the reference to breeding. My memory had confused Hubbell's observations of harvestmen with her observations of captive camel crickets, described in Chapter 13. Deor (talk) 03:49, 18 August 2009 (UTC)

Wow! Thanks! Now I also get to read the article rhaphidophoridae, I find two in the room per day. Mac Davis (talk) 05:23, 18 August 2009 (UTC)

What is the opposite of a "Ploughman's lunch"?Edison (talk) 04:27, 19 August 2009 (UTC)

Fruit on an empty stomach

Hi All,

Got one of those forwarded emails, and I was intrigued at it's claim that fruits are best eaten on an empty stomach. It claims that though the fruit in question might be acidic (say a pineapple) in taste, the email claims that it turns basic once it interacts with digestive juices.

I do personally recall eating grapes on an empty stomach a few weeks ago and not really suffered anything, I was wondering if that was a fluke or does this claim have really have a scientific foundation? If its true what's the chemistry behind it? I (sucking at chemistry) would have assumed that acid + acid = more acid.

Please forgive my ignorance. :P Thanks in advance! PrinzPH (talk) 02:42, 18 August 2009 (UTC)

It sounds like nonsense to me. I eat fruit both on an empty stomach (for breakfast) and a full stomach (for desert) most days and don't have any problems. What did the email say would go wrong? --Tango (talk) 02:47, 18 August 2009 (UTC)

Well it claimed that eating food along with meats and other stuff would cause the other food to putrefy (is that the right term?) and cause gas. It also made claims that it (other food item) might absorb some of the nutrients that our body would have otherwise absorbed. PrinzPH (talk) 02:58, 18 August 2009 (UTC)

Gas varies from person to person and isn't usually harmful, so trial and error is the best approach there - if you find a combination of foods that gives you gas, you may want to stop eating that combination, otherwise don't worry about it. As for nutrients, it sounds unlikely - your body is going to absorb the other food as well, so at worst it will delay the absorption of the nutrients. I guess it is possible the nutrients will be absorbed by part of the other food that can't be digested and just goes straight through you, but it doesn't seem likely. Did the email give any kind of clue as to the source of this information? --Tango (talk) 03:04, 18 August 2009 (UTC)

It sounds like Fit for Life but I believe that there are other diets with similar ideas.Sjö (talk) 13:00, 18 August 2009 (UTC)

Sorry don't really recall too much (deleted it after giving it a once-over). Tango's explanation does make sense, I guess in the end it really boils down to individual reactions. I'm still curious though about how our digestive juices interact with food acids.. Anyone got an article to point me to? PrinzPH (talk) 18:05, 18 August 2009 (UTC)

There are two pretty good online sources at food combining. Livewireo (talk) 19:47, 18 August 2009 (UTC)

Go to www.snopes.com type "eating fruit" in the search field and you will find your answer.

Transcendental Meditation and stress accumulation

My question is twofold:

1. A friend of mine started talking to me about how great transcendental meditation is and how it has changed him. From what he described it sounded like a cult (an immensely expensive one) and he insisted on telling me some anecdotal evidence which I dismissed. The Wikipedia article does sound like it has some benefits but some parts of it sound confusing- does TM have any real benefits, and if so are they greater from the benefits of say lying down or simply meditating normally? I tried looking for facts on the Internet but only found sources but only found sources by the TM company claiming some 500-600 studies done by 250 separate universities- is that true?? The number of studies sounds incredibly high! And all of the results I saw were way too good, and I couldn't help but thinking about bogus infomercials.
2. At some YouTube video discussing the awesome results of TM (uploaded by the TM company) John Hagelin said that the "that about 90% of diseases are caused or complicated by stress" and then said something about "stress accumulation". Is that "90%" part correct, and is there such a thing as accumulative stress (I've heard that term many times)? Stress isn't an object (as far as I know) but rather a state of mind- wouldn't you rather talk about some of the psychological and biological harm that a person suffers from too much stress?

Am I just a paranoid sceptic? At first I was going to mention how John Hagelin did not sound like a doctor at all (because he seemed way too certain and used too many absolutes) but he has a lot of credentials so I'm not too certain. I honestly don't know what to think, everything I hear about this screams cult and pseudo-science but yet it seems to check out.. --BiT (talk) 02:52, 18 August 2009 (UTC)

Oh and apparently the Ph.D. made an apperance in What the Bleep Do We Know!? which appears to be bullshit, but he was a researcher at CERN, a Professor of Physics and Director of the Institute of Science, Technology and Public Policy at Maharishi University of Management.. wait Maharishi University of Management was founded by Maharishi Mahesh Yogi, who introduced the Transcendental Meditation technique.

The plot thickens! --BiT (talk) 03:00, 18 August 2009 (UTC)

There is no thick plot and you are right, it is a cult and a pseudo-science. The only reason the plot appears thick is because the amount of money that is spent by TM on marketing. Do you think there are no people with "real and legit" credentials who would claim some rubbish for a high enough price? Or even if they aren't shilling, maybe there even are a few smart and well meaning people who do actually believe it, for some reason, that doesn't prove anything. If the claims were published in a peer reviewed journal, THEN is when I would start taking it seriously. And claims like "90% of diseases are caused or complicated by stress" mean nothing. Maybe 10% (purely for arguments sake) are caused mostly by stress and who would argue that excessive stress is a bad state to be in if you are sick already? The vast majority of the claims they make however are not so "ambiguous", they claim to influence world events with their "meditation", and that is definitely BS. Something funny I heard recently was when the Christian scientists at answering genesis came up with a petition of 300 scientists who "doubt evolution" (that list was found to be complete BS anyway). In response Project Steve was set up which gathered over ONE THOUSAND scientist with the given name Steve who support evolution. Without a context, those kind of claims made by TM mean absolutely nothing. And "what the bleep do we know" is complete rubbish, the whole thing was a promotion of the teachings of JZ Knight who under any rational definition is a complete loony and should have probably got medical help a long time ago. In any less libreal society she would have been thrown in a loony bin or burned at the stake for being a witch.. Not that I would condone the latter, but i'd probably not protest against the former. Vespine (talk) 04:32, 18 August 2009 (UTC)

Since "If the claims were published in a peer reviewed journal, THEN is when I would start taking it seriously", I have some shocking news to deliver: Transcendental_meditation#Research describes a number of studies published in genuine peer-reviewed journals concerning the physiological effects of transcendental meditation, some of which demonstrated significant results. Furthermore, it's high time that we end the practice of characterizing new religious movements as "pseudosciences": a pseudoscience necessarily involves a theory with pretensions towards science. Religions and spiritual theories aren't sciences, pseudo or otherwise. The existence of scientific studies regarding the effects of TM doesn't alter this basic framework, any more than studies of the physiological effects of Christian prayer would transform Christianity into a pseudoscience. Erik9 (talk) 05:05, 18 August 2009 (UTC)

The question of "cult" status is, perhaps, a more difficult one, discussed at Transcendental_Meditation#Cult_issues. Erik9 (talk) 05:18, 18 August 2009 (UTC)

Hang on what? I wasn't characterizing it as pseudoscience just because it was a new religion, it doesn't actually claim to be a religion. All of the apparently legit studies simply monitored the effects on things like blood pressure of the actual practitioners of TM, this isn't compared to studies of other types of meditation so I'd consider it completely useless as an indicator of anything. I guarantee there isn't an independent double blind study confirming a blood pressure difference in people who are in a room alone, where one group has TM people in the next room focusing their effort on them, and another control group has no one focusing "TM energy" on them. I guarantee such a claim would and could not be proved, but that is in effect what TM is trying to suggest with its pseudo-science claims such as this: http://www.tmprogram.com.au/charts/chart_51.html and this http://www.tmprogram.com.au/charts/chart_49.html complete garbage. Vespine (talk) 06:31, 18 August 2009 (UTC)

Ok I've actually read a bit more of the TM article because I'm actually interested in religions and science and and stuff like that. So there have been some studies which show some kind of positive effects of TM, ON THE PRACTITIONERS of TM. With respect to things like blood pressure, quitting smoking and even learning at school, but most of these studies are on people who already practiced TM or intended to study TM, so the motivation of these people can't be ruled out either (the control groups would have less motivation to do any better). But there are also many studies which show no effect, or very little effect, or effect comparable to that of other kinds of meditation. This is nothing surprising really. What there is none of, like I said above, is any kind of study showing that practitioners of TM have any kind of effect or influence on external things like the road toll, or war fatalities, which is exactly what TM claims to be capable of. They throw the bath water in with the baby, if I can reverse that saying, they attempt to use the scientific studies about "TM making you feel nice if you meditate" to validate their completely ridiculous claims of what else they can do. Pseudo-science through and through. Vespine (talk) 06:52, 18 August 2009 (UTC)

It's pretty obvious that stress is a major contributor to bad health of all kinds. It's also pretty clear that sitting down for a while, trying to forget your problems and generally relaxing is a way to (at least temporarily) relieve stress. So it's no stretch at all to believe that TM does indeed make you somewhat healthier, perhaps somewhat happier. However, the pseudo-science kicks in with all of the very tightly specified methods and attendant BS that comes with TM. What makes it a "pseudoscience" is that they use all of the trappings of science - but without any of the scientific methods. They started with a technique and then tried to justify it. In science, we study the problem and develop techniques to solve the problem. As our article points out, TM "experts" make all sorts of claims that are essentially unjustified - and it's pretty evident that simply relaxing, "going to your happy place", doing something to take your mind off of stress at work, etc, is what's doing you good. If you have to have all of the chanting and quasi-religious BS in order to do that - well, maybe it has some benefit. You could easily imagine the busy housewife with a handful of noisy, annoying, demanding kids running around the house gaining benefit from saying "Mommy is doing her TM now - that means you've all got to be quiet for half an hour and leave her alone." - compared to simply trying to relax amongst all of the chaos. Merely giving the technique a name may confer benefits that more obvious and informal relaxation cannot. However, the multiple days of (expensive) training and the mystique that's wrapped around TM is clearly just a means to extract money from gullible people. SteveBaker (talk) 11:43, 18 August 2009 (UTC)

I don't know about any spiritual claims, but I found the technique capable of completely blocking all pain from a tooth abscess when I was waiting for dental treament and had run out of (nowhere near as effective) painkilling drugs. I was even able to BITE on the absess-unthinkable even with painkillers. I had to maintain the lotus position to keep this self hypnosis up-deviating from it brought the pain back.Trevor Loughlin (talk) 12:42, 18 August 2009 (UTC)

At a minimum it could give a placebo effect. Googlemeister (talk) 14:41, 18 August 2009 (UTC)

So doing TM is tantamount to relaxing/taking a break? --BiT (talk) 15:11, 19 August 2009 (UTC)

And regarding the second part of my question- can stress accumulate? --BiT (talk) 15:11, 19 August 2009 (UTC)

Of course stress can accumulate. That is why some stressful jobs have such high turnover rates. Googlemeister (talk) 18:51, 19 August 2009 (UTC)

Trevor, you didn't even need a painkiller? Then you were able to transcend dental medication! Bunthorne (talk) 10:01, 20 August 2009 (UTC)

Oh snap, very nice, lol. Vespine (talk) 23:39, 20 August 2009 (UTC)

Fast acting diseases?

A staple of Sci-fi and other drama is the quick acting viral/bacterial infection, where the victim seem to go from first contact to death in a matter of minutes to seconds. Is that possible real life? If not, what would have to be different about the viruses and bacteria to make this possible?

Thanks in advance —Preceding unsigned comment added by 99.240.189.90 (talk) 06:21, 18 August 2009 (UTC)

The rate of growth of either a bacterial or a viral infection is limited by the rate at which cells can divide and then grow large enough to divide again. For bacteria it's the bacteria that do this; for viruses it's your own cells that the virus has taken over. Presumably the real-life diseases with the shortest incubation times, which I think are on the order of a day or two, represent the fastest that is possible in that regard. --Anonymous, 08:25 UTC, August 18, 2009.

Not sure how fast acting it is, but botulism is pretty quick (maybe on the order of hours?). That is a byproduct of certain bacteria, not the bacteria themselves. Googlemeister (talk) 13:12, 18 August 2009 (UTC)

I'd guess that diseases could kill in minutes or hours (but probably not seconds), but there's no evolutionary path there as killing your host quickly is a poor survival strategy for a virus or bacteria. Ideally they should keep the host alive for a long time so they spread the disease to others. If they even prevent the host from reproducing, then the host animals which are susceptible to the disease will be selected against, which will result in an immunity to the disease over time (as happened to Bubonic Plague, for example). However, some evil scientists doing genetic engineering might be able to come up with such a virus or bacteria. It would need some strategy for defeating the immune system of the host body, though, such as appearing to be normal cells. StuRat (talk) 13:24, 18 August 2009 (UTC)

Bacterial endotoxin released when the bacteria are lysed by the immune system, and bacterial exotoxin released by the bacteria themselves probably play a big role in the rapid decompensation (septic shock) that is sometimes seen in people with bacterial illnesses. However, in agreement with others, this process takes more than a few minutes, maybe on the order of hours to days depending on the severity of the infection, host's immune system, and other factors. In viral illnesses, you may sometimes see a cytokine storm that results from an overactive immune system and can be just as devastating as septicemia. --- Medical geneticist (talk) 13:55, 18 August 2009 (UTC)

I believe there are neurotoxins that can kill in absurdly small doses. If a bacteria produced one, it probably could kill someone that fast. Of course, then you might as well skip the bacteria and say that they got neurotoxin on them. — DanielLC 15:11, 18 August 2009 (UTC)

Prolly you could get a pathogen that triggered such a vigourous immune system response that their own immune system kills them. John Riemann Soong (talk) 16:02, 18 August 2009 (UTC)

Something that fast-acting would need to depend on something that is already present in the body. Consider a benign virus that somehow causes teh host to generate a precursor chemical that auocatalytically converts to a fast neurotoxin. Consider a second agent (a bacterium, perhaps) that propagates benignly until some envronmental condition causes it to emit a few molecules of the neurotoxin. The resulting autocatalytic cascade would flood the body in seconds. This would need to be engineered, as there is no reason such a system would arise as the result of natural selection. -Arch dude (talk) 16:34, 18 August 2009 (UTC)

I think a key question is whether this virus was naturally selected -- i.e. in accordance with selfish gene theory and zombies, or artficially selected by say, (controlled by an evil scientist). In a naturally-selected case of death within minutes, the pathogen's ideal host is probably a different species (say, an elephant) -- where it must act extremely virulently to avoid being suppressed by the elephant's immune system, but is too virulent in humans. The naturally-selected case is IMO the more frightening one (one good for a horror film) because the pathogen appears to have a will of its own ... and the best (most horrifying) timeframe would be death within a day, leaving time for the infected individuals to pass on their pathogen to other humans.

There are also not many mechanisms of death (besides just sheer violence) that would kill someone within minutes. A few things I can think of:

• Anaphylaxis
• Blood pH -- acidosis, alkalosis -- if key cells with a large influence over pH (kidneys, acid-releasing glands, etc. are compromised)
• Intercell apoptotic cascade in a few critical areas (suppose you got a small part of the stomach wall to suddenly undergo mass cell death, for instance...)

There's also a rather improbable mechanism, yet plausible enough for me to have suspension of disbelief during a sci-fi horror film. You basically have inactive proviruses stored within the genome ... lots of them. Now say there was one nicely embedded in a region that was shielded from DNA damage, or located next to some critical coding region, and maybe has an active DNA repair portion helping to keep the virus' integrity in check; if mutation in this region occurs, the cell undergoes apoptosis. Now, all you have to do is administer a little systemwide "signal" into the bloodstream that will trigger this provirus out of latency; cells everywhere in the body would suddenly activate viral replication ... John Riemann Soong (talk) 16:36, 18 August 2009 (UTC)

On second thought, we actually have a lot of active proviruses (active for our species, I mean, not in adults). They get activated during gestation (evolution has converted their virulent properties for other purposes, like preventing the mother's immune system from attacking developing young). As a result these proviruses are probably conserved. As a matter of fact, we have a lot of other "malicious" DNA as well (used for things like programmed cell death or phagocytosis); you could have a pathogen which would trigger such cascades. PCD and apoptosis by themselves evolved from "pathogens" as well -- we now see mitochondria and chloroplasts as "friendly" to the bigger eukaryotic cell of course, but once upon a time they were enemies. John Riemann Soong (talk) 16:50, 18 August 2009 (UTC)

Monitoring wireless

Can I monitor website visits by those who use my wireless? 173.54.205.131 (talk) 11:58, 18 August 2009 (UTC)

Yes, I believe you can use applications like Wireshark to monitor what websites computers that are using your wireless network are accessing.--droptone (talk) 12:21, 18 August 2009 (UTC)

Is there a way to block this? --Reticuli88 (talk) 12:27, 19 August 2009 (UTC)

You cannot truly prevent packet sniffing without preventing your own devices from communicating, but there are three practical ways to "block" it. The first is physical— it is to ensure that your broadcast area does not reach places you do not want it to through strategic placement of access points and physical barriers to signal. The second is to encrypt your communications so when the person watching your data picks it up, they can't actually understand it. The third is to prevent them from knowing your network exists at all, like making sure the SSID is not broadcast. Only the physical security may stop a knowledgeable and determined person. Mac Davis (talk) 04:09, 20 August 2009 (UTC)

Photo diode question

is it posible an AVALANCHE PHOTODIODES to detect metals like cuper or gold?Sakis1964 (talk) 13:01, 18 August 2009 (UTC) Tank you very much

No. Is there any reason you thought it would? , or is it "shit and run" as usual?83.100.250.79 (talk) 17:29, 18 August 2009 (UTC)

Connecticut residence of Samuel Finley Breese Morse

Am attempting to track down specific dates (and any other related informtion) when Samuel F.B. Morse lived in Connecticut, specifically Saybrook, CT (probably when he was at Yale). Any information or references appreciated. 99.33.198.140 (talk) 13:40, 18 August 2009 (UTC)

KINEMATICS

This is my homework question. Please find where have I mistaken Here's the question:

A cylinder rolls without slipping over a horizontal plane. The radius of the cylinder is equal to r. Find the curvature radii of trajectories traced out by the points A & B. Point A is the topmost point(on the cylinder's circumference), whereas ,point B is at a distance r from the ground on the circumference of the cylinder.

What I did was, consider the cylinder to roll with velocity v. Then every particle on its circumference will have velocity v.

consider the trajectory of bottom-most point on the circumference. It willbe having constant velocity throughout.

consider downward acceleration to be a & along positive X axis to be b.

the maximum height is 2r & range is 2πr. Let the angle made by the projectile with X axis be Φ.

Solving , I got a=v²sin²Φ/(4r) & b=v²sin²Φ/(2πr) & (1-cosΦ)/sinΦ=b/a

From these three equations I got cosΦ=1 or cosΦ=(π²-4)/(π²+4) cosΦ=1 is neglected.

Now, at the topmost point of the trajectory, vertical forces are balanced. Therefore, mass*a=mass*v²/R° [Where R° is the radius of a very small arc near point A] Therefore , I get R°=4r*(π²+4)²/(16π²) But the answer is R°=4r & the radius at point B =2√2r which I am getting as R=4√2rπ/(2+π) Please tell me what is wrong in this method. —Preceding unsigned comment added by 121.245.182.159 (talk) 15:24, 18 August 2009 (UTC)

Unless I'm picturing the scenario incorrectly, some of your statements are false, especially "every particle on its circumference will have velocity v". The bottom point in particular always has an instantaneous velocity of zero, since the cylinder is rolling without slipping.

Cycloid. Cuddlyable3 (talk) 19:40, 18 August 2009 (UTC)

Eventhough this is homework, I think you seem to have put enough effort into it to deserve some help. The 'slick' way to do that problem is to move back and forth between two different reference frames. The first reference frame is the one where the ground is at rest and the cylinder moves with speed v henceforth RF1. The second reference frame would be the one where the cylinder is at rest and the ground is moving (back) with speed v henceforth RF2. The relative velocity between the two reference frames has magnitude v and you have to (vectorially) add (subtract) that velocity to a particle's velocity to go back and (forth) between the two reference frames. Your statement that all points on the circunference have the same speed is true in RF2: |VA2| = |VB2| = v. But that's not the case in RF1 because of the (vectorial) additions: VA1 = VA2 + Vrel and VB1 = VB2 + Vrel where Vrel is the relative velocity between the two reference frames. For the point A VA2 and Vrel are parallel and you get |VA1| = 2v. For the point B VB2 and Vrel are perpendicular and you get |VB1|= (√2)v. I will do the easy one (point A) for you and leave the hard one (point B) for you to do yourself. in RF2 we have the relationship between speed, radius of curvature, and centripetal acceleration: ac = |VA2|^2/R2 = v^2/r = . That acceleration is also perpendicular to motion in RF1 (that's not true for the point B and that's what makes that point harder. You will have to find the centripetal component of the acceleration to work out point B), so you also have the relation ac = |VA1|^2/R1 = (2v)^2/R1 = 4v^2/R1. R1 is the radius you are trying to find. Put the two expressions for ac together we have ac = v^2/r = 4v^2/R1 which simplifies to R1 = 4r as desired. Dauto (talk) 16:48, 19 August 2009 (UTC)

brain blood barrier

If you can remove some CSF with a lumber puncture why cant you add medication with the same method and bypass the brain blood barrier.D4n5er (talk) 16:35, 18 August 2009 (UTC)

Medications can indeed be given using lumbar puncture (called intrathecal injection), such as spinal anaesthesia and some chemotherapy drugs such as methotrexate. Axl ¤ [Talk] 17:03, 18 August 2009 (UTC)

But the method is generally too risky to use on a routine basis, besides being extremely painful. Any puncture of the membranes around the brain or spinal cord creates risks of infection or leakage, either of which can pretty easily lead to paralysis or even death. Looie496 (talk) 17:28, 18 August 2009 (UTC)

• "Extremely painful"? Done properly, it should not be extremely painful.
• "Any puncture of the membranes around the brain or spinal cord creates risks of infection or leakage." This is true, but again if done properly the risk is low. CSF leak is usually fairly easy to treat.
• "... either of which can pretty easily lead to paralysis or even death." This is certainly not true. Read this article.

Axl ¤ [Talk] 17:54, 18 August 2009 (UTC)

You can...but it would not nearly as easy a route as oral, subdermal, intramuscular or even intravenous administration. DRosenbach ^{(Talk | Contribs)} 02:49, 19 August 2009 (UTC)

Spherical coincidence

Can you visualize energy as the surface of a sphere having the diameter squared of the distance light travels in one second when mass is equal to pi? -- Taxa (talk) 16:51, 18 August 2009 (UTC)

No I can't - because parts of what you wrote seem meaningless - I got as far as a sphere. Can you clarify from "diameter squared" onwards.83.100.250.79 (talk) 17:28, 18 August 2009 (UTC)

I hate to say it, but I can actually make sense of this. Taxa is observing a parallel between $E=mc^{2}$ and $A=4\pi r^{2}=\pi d^{2}$. Of course, it should be the speed of light, not "the distance light travels in one second"; how would you pick "one second" out of all the possible lengths of time? Since Einstein's observation is that energy is proportional to mass (via the constant $c^{2}$), and the sphere formula gives area as proportional to diameter squared (via the constant $\pi$), I don't see any worthwhile correlation: the constant in one expression "corresponds to" the crucial variable in the other. --Tardis (talk) 17:39, 18 August 2009 (UTC)

Agreed, and for the purpose of developing an analog, the "squared" isn't so important as a constant is being squared, so I would be more simple-minded and use any old linear relationship to visualize. But yes, for a constant mass and a sphere with c diameter, the initial observation would work. Awickert (talk) 19:47, 18 August 2009 (UTC)

You can visualize anything you want - but this particular thought experiment seems to have no useful physical interpretation. In the case of mass-energy equivalence, there's not a relevant analog to "surface area of a sphere" - so I can't think of any reason to use such a geometric model. Did you have any particular reason or expected consequence for comparing that equation? There are plenty of other geometric equations which have a similar algebraic representation, but that doesn't mean they're in any way physically relevant. You might want to read about dimensional analysis for a better way to think about the units involved - you might actually come up with some more useful analogies by picking similar equations with similar units. Nimur (talk) 06:35, 19 August 2009 (UTC)

Blood pressure and emotions

Do blood pressure measurements vary based on a person's emotions such as when a person is sad, happy, angry or nervous? And if so, by how much at the most? Thank you. Clover345 (talk) 16:53, 18 August 2009 (UTC)

Yes, blood pressure does vary with emotion. Indeed there is a syndrome called "white coat hypertension" where blood pressure rises solely because of attendance at a doctor's clinic. Axl ¤ [Talk] 17:09, 18 August 2009 (UTC)

Have a look at this article.

Mean change in blood pressure with emotion-related imagery

Parameter	Happiness	Sadness	Anger	Fear	Control	Relaxation
Diastolic blood pressure	+3.6	+1.7	+6.9	+3.4	+1.5	-0.9
Systolic blood pressure	+5.0	+6.4	+7.3	+6.7	+0.5	+0.6

Axl ¤ [Talk] 17:25, 18 August 2009 (UTC)

Thanks. It says in one of your articles, that hypertension derived from emotions or "white coat hypertension" as its called can lead to actual hypertension. Is this as a direct result of blood pressure rising at such times or is it the emotions that cause blood pressure to rise in the long term? Surely if raised blood pressure dut to emotions can lead to actual raise blood pressure, then raised blood pressure as a result of physical activity can also have the same effect.Clover345 (talk) 17:38, 18 August 2009 (UTC)

I've also got to think that the sphygmomanometer itself must raise your BP, as it's about as pleasant as having a boa constrictor coiled around your arm and squeezing. StuRat (talk) 20:52, 18 August 2009 (UTC)

I had a look through the literature. I couldn't find any information on the progression of white coat hypertension. There's no clear evidence looking for the development of sustained hypertension. The potential benefit of treatment is controversial. See these articles: White-Coat Hypertension and Risk of Stroke & "White coat hypertension — should it be treated or not?". Axl ¤ [Talk] 21:03, 18 August 2009 (UTC)

To StuRat: the gold standard for blood pressure measurement is the arterial line. According to this article, "the direct [arterial line] and indirect [sphygmomanometer] methods yield similar measurements, but these are rarely identical because the direct method measures pressure and the indirect method is more indicative of flow. The indirect method is generally less accurate and less reproducible. Nevertheless, it is sufficiently accurate for many diagnostic and therapeutic studies." From this article: "Compared with direct intra-arterial measurement of blood pressure, the auscultatory technique using Korotkoff sounds tends to give systolic values that are slightly lower and diastolic values that are slightly higher than intra-arterial measurements." Axl ¤ [Talk] 21:24, 18 August 2009 (UTC)

I should think a painful arterial line would cause even more stress and thus higher BP. So how exactly do they know that it's more accurate ? StuRat (talk) 00:11, 19 August 2009 (UTC)

Arterial lines can be left in for days, during which time they are not constantly a source of discomfort, so they would not be expected to affect BP. One does have to be cautious about using arterial lines as a gold standard, because systematic measurement error can be introduced by phenomena like under-damping, which can cause artefactual elevation of systolic and depression of diastolic readings. --Scray (talk) 03:55, 19 August 2009 (UTC)

Also, exact blood pressure is not important. We are looking at comparison of blood pressure. Assume that the measuring device increases everyone's blood pressure by 10%. We would be comparing those with high blood pressure to those with normal blood pressure - with both values raised 10%. No problem. Further, if a person's blood pressure is raised abnormally by the measuring device, it is safe to assume that the person reacts similarly to other things. in other words, the person has repeated spikes in blood pressure throughout the day. This is intermittent hypertension and is very difficult to treat. If you control the spikes, blood pressure will be too low between the spikes. In the end, it isn't really a hypertension problem. It is an emotional problem that must be dealt with from a completely different expertise. -- kainaw™ 15:46, 19 August 2009 (UTC)

• "Assume that the measuring device increases everyone's blood pressure by 10%." This assumption is incorrect.
• "If a person's blood pressure is raised abnormally by the measuring device, it is safe to assume that the person reacts similarly to other things." Another inappropriate assumption.

Axl ¤ [Talk] 16:44, 19 August 2009 (UTC)

I had similar thoughts. Someone accustomed to medical procedures might not have any BP spike at all, while for someone else, who is normally calm, but with an absolute phobia of doctors, a sphygmomanometer or, God-forbid, an arterial line, may cause an all-out panic attack. StuRat (talk) 14:20, 20 August 2009 (UTC)

Airport Security & Philosophy

Why do airport security signs use the term "your person"? As in "Please remove all non-permitted materials from your person."

Has the Transportation Security Administration implicitly declared their adherence to the philosophy of Dualism? TheFutureAwaits (talk) 17:50, 18 August 2009 (UTC)

I believe the implication is that "your person" is broader and more encompassing than other terms such as "your body," "your clothing," or "your baggage." Saying "your person" is saying anything you feel is currently connected to you via ownership. ~ Amory (user • talk • contribs) 18:49, 18 August 2009 (UTC)

There's sort of a "formal language" which seems to be in use in law-enforcement-style communities (though the TSA is not a law enforcement agency properly - it's sort of similar in scope). I think it has to do with politeness, and treading delicately with words in what might otherwise have serious legal ramifications. (If the sign said "no contraband on your body" it's leaving a legal loophole for contraband in your pocket, for example). This legal liaison organization suggests that the use of such language has a sociological consequence of creating a power-imbalance between the citizen and the Officer - they claim that "verbal cues, which may include the use of technical jargon or a military-like formality in the use of language, contribute to perpetuating this power imbalance." Nimur (talk) 06:42, 19 August 2009 (UTC)

Why shouldn't there be a "power imbalance" between the citizens and the officers? They're in charge, they have the legal authority, why shouldnt they act like they're the boss? I mean, when a traffic cop gives you a ticket for speeding, do you complain that there's a "power imbalance" between you and the cop? That's just the way things are, get used to it. 98.234.126.251 (talk) 07:00, 19 August 2009 (UTC)

Nimur did not say that there should not be this power imbalance in such situations, he/she merely presented evidence that it exists. Try to vent your spleen towards the appropriate targets. 87.81.230.195 (talk) 11:28, 19 August 2009 (UTC)

Hmm, it seems like most of these answers skirt around my original question. What I'm getting at is when the signs state "your person" they are implicitly indicating that you own your person and that "you" are something different than your person. As in the ethereal consciousness of your being should be aware of the need to remove objects in the possession of your physical body.

Therefore, regardless of the formality of the term, the TSA is taking a stance on a philosophical issue by stating "you" are independent of your body (i.e. dualism). Is this position not logical? TheFutureAwaits (talk) 15:39, 19 August 2009 (UTC)

Not really. I doubt that the TSA has any such official philosophical stance for or against dualism. Their mission is not to debate the philosophy of mind; it's to "protects the Nation’s transportation systems to ensure freedom of movement for people and commerce." [1]. From the very few words on the sign, you're extrapolating quite a bit of philosophy. The word-choice on the sign is probably, as I mentioned above, more about legal formality than philosophical belief. If you're curious about the institutional philosophy and official positions of the TSA, reading signs in airports will be less instructive than reading their mission statement and self-descriptions, available here. And regarding the above comments - I endorsed no position; I merely found a description of the language from the web. I think the OP might appreciate the subtlety of word-choice in this context, because a warning sign at an airport is not really the same as a philosophical rumination.Nimur (talk) 15:53, 19 August 2009 (UTC)

Line

On particularly athletic bodies (I've only ever seen it on males but it could be on females as well) there is a line that curves upwards just by the kidneys, slightly above the waist. Could someone tell me the name of this line? Cheers. 92.3.166.124 (talk) 18:16, 18 August 2009 (UTC)

I've only ever heard them called "groin lines" in life, although I found a book that might help. The picture there (p. 24) lists some lines, and although it's not quite clear which exactly are which, it could be a combination of the femoral fosset and the Demicircular line. ~ Amory (user • talk • contribs) 19:00, 18 August 2009 (UTC)

I assume you are refering to Apollo's belt aka the iliac furrow that runs from the hips to the groin? --Jayron32 20:50, 18 August 2009 (UTC)

The OP is referring to a line above the waist and curving upward, this is not the iliac furrow which is below the waist and runs down from the waist. I think he is referring to the outside edge of the latissimus dorsi muscle, also visible in this diagram.[2]. I am not aware that this line has any special name. 86.4.181.14 (talk) 08:05, 19 August 2009 (UTC)

more direct link —Tamfang (talk) 19:37, 6 December 2009 (UTC)

Extracting ricin from castor beans

A recent episode of Breaking Bad had Walter extracting Ricin from Castor beans. As a chemistry teacher, I know that he probably has the know-how to do that, but my question is, how easy is it for a layman to obtain Castor beans? He lives in New Mexico. Who then was a gentleman? (talk) 18:56, 18 August 2009 (UTC)

It is used as a decorative plant. It is not difficult to obtain, as you can just grow them. Now if you need 500 lbs of the beans to extract a small amount of the toxin, that is a different story, but if you just need a few beans, no difficulty at all if you live in a warm climate. Googlemeister (talk) 19:08, 18 August 2009 (UTC)

(ec) Too easy? The article says: "Ricin is easily purified from castor-oil manufacturing waste. The aqueous phase left over from the oil extraction process is called waste mash. It contains about 5-10% ricin by weight. Separation requires only simple chromatographic techniques." As to how easy one might actually find that, well, take a look at the patent (pdf). None of that is particularly complex or difficult to acquire, although high school or college level Chemistry courses (especially Organic chemistry) would make it a lot easier to understand, prepare, and follow. Still, it seems to be simply a matter of getting the reagents, glassware, and castor beans. ~ Amory (user • talk • contribs) 19:10, 18 August 2009 (UTC)

It's harder not to extract ricin than it is to extract it. When making castor oil you have to ensure that none of the ricin ends up in your oil. Just a few beans can kill you, so you shouldn't need too many. You don't even have to purify your extract. John Riemann Soong (talk) 19:25, 18 August 2009 (UTC)

Is somebody trying to manufacture chemical weapons here?! 98.234.126.251 (talk) 22:45, 18 August 2009 (UTC)

Ricin is not much of a chemical weapon; it is a poison. You could potentially take a LOT of it and drop it on people, but, as our article points out, it's not any more effective than dropping any old poison in quantities on people. It's more poisonous than, say, rat poison, but the same principle applies. The media gives it a lot of hype, but it's not necessarily all that worse from a security perspective than, say, arsenic, except for the fact that it is easy to get castor beans (though it's not hard to get rat poison, either). From a security perspective, it's a lot less worrying than, say, ANFO. --98.217.14.211 (talk) 01:15, 19 August 2009 (UTC)

Well what if some terrorist bastard decides to poison the water supplies with ricin, wouldn't that be chemical warfare too? 98.234.126.251 (talk) 07:02, 19 August 2009 (UTC)

Sure. But there's a ridiculous number of substances someone could use to poison water supplies. Ricin is by no means the most effective, or even the most readily available. Hell, you could just have all your terrorist friends empty their terrorist bowels into a huge plastic sack, let it fester for a while, and then dump the contents into the water supply, and you've got some homegrown chemical warfare right there. Super effective? Probably not, because the payload would end up very much diluted, but the same thing certainly applies to ricin as well. You'd have to get a lot of it for it to be effective -- or even noticeable, really. Poisoning the water supply isn't a very effective delivery method for all sorts of reasons. -- Captain Disdain (talk) 09:18, 19 August 2009 (UTC)

I saw a Musselman purchasing a dietary fiber supplement. Should I be worried? --Sean 16:11, 19 August 2009 (UTC)

With all due respect to Muslim terrorists, historically, the most significant ricin usage has been by "white people": Americans, Bulgarian communists, and Canadians - far more often than it has ever been used by Islamic terrorists. It's sort of worrisome that 98.234.126.251's kneejerk reaction is to suspect a particular religious community who (for all intents and purposes) have no association with this particular tactic. I think this is called racial profiling - and not very good profiling, either, as it fails to account for historical precedent. Nimur (talk) 16:45, 19 August 2009 (UTC)

With all due respect to Nimur, not all Muslims are Arabs. Iranians are caucassian. There are white people who adhere to Islam. Googlemeister (talk) 20:45, 19 August 2009 (UTC)

Have there been any significant instances of Islamic terrorism related to ricin? 98.234.126.251's link suggests he is concerned about motherless Muslims. Our article lists several cases of ricin-related incidents, and none of them appear at all related to Islamic terrorism or bastards. Maybe race, religion, family status, etc., have no correlation to ricin (I think that's a reasonable conclusion, no?). Nimur (talk) 21:50, 19 August 2009 (UTC)

Nimur -- how dare you accuse the American people of using ricin for criminal purposes without providing examples of non-Muslim Americans doing that? I challenge you to give me some examples of that; if you can't find any, then your comments are defamatory toward the Americans and you gotta take them back. 98.234.126.251 (talk) 00:47, 20 August 2009 (UTC)

Ok, there were a few examples, according to the article. I stand corrected on that count (but stand by my other statements). 98.234.126.251 (talk) 01:20, 20 August 2009 (UTC)

As for an example of Islamic terrorism related to ricin -- back in January 2003, six Arab muslims were arrested in London for trying to poison the water supply with ricin. Also, the article actually does mention several instances of islamics (Algerians, Kurds, Chickens, etc.) plotting to use ricin to murder people. Did you intentionally overlook these examples because they contradicted your pre-conceived notion that none of the ricin-related incidents were instigated by muslims? 98.234.126.251 (talk) 00:53, 20 August 2009 (UTC)

And BTW, when I said "bastards", I did not mean it in a literal sense -- so your assertion that I'm somehow insinuating a correlation between family status and a propensity toward terrorism is completely baseless. As for correlation between religion and terrorism, if you haven't noticed that the vast majority of terrorism is carried out by islamics then you've got your head buried in the sand (and that's putting it mildly). 98.234.126.251 (talk) 00:58, 20 August 2009 (UTC)

I hope you realize that the vast majority of acts of terrorism on American soil have been committed by Americans, though. Our category of Terrorist incidents in the United States, though by no means complete, should give you an idea. Not that I'm saying that islamic terrorism isn't a concern, but frankly, at this point you're blatantly soapboxing. -- Captain Disdain (talk) 06:04, 20 August 2009 (UTC)

What acts of terrorism are you talking about? I challenge you to give me some examples, and if you can't then you gotta take your statement back. 98.234.126.251 (talk) 09:18, 20 August 2009 (UTC)

I've just taken a look at the article History of terrorism -- the only American terrorist groups listed there are the Ku Klux Klan and the Weather Underground, while the Islamic terrorist groups (from the Assassins to Al-Qaida) are too numerous to count. 98.234.126.251 (talk) 09:39, 20 August 2009 (UTC)

Apologies: I did give some examples, but I screwed up the link. It's fixed now in my post above. The point is, domestic terrorism is no joke: white supremacists, non-Islamic religious fanatics and just plain old crazy people get around, and their actions have included murders, bombings, plane hijackings, and, yes, even ricin letters. Perhaps a part of the problem here is that these days, a lot of people think "terrorism" means "attack on America by Muslims", or "attack against another country", or "politically or religiously motivated attacks", or some variation thereof. But it doesn't. It just means doing something to scare the fuck out of people in order to get them to do what you want, or even just to make a statement. The 9/11 attacks where a horrible thing, absolutely, but they were really, really exceptional when compared to the "average" act of terror. Most acts of terror are fairly small, because generally, that's the point of engaging in terrorism: you do a relatively small thing, and you scare everyone who hears about it. Those Christians who bomb abortion clinics or murder doctors who perform abortions? They're terrorists, plain and simple. Terrorism is cheap, easy and efficient, because it's unpredictable and often very hard, if not impossible, to defend against. I mean, at its most extreme, there's pretty much nothing you can do to keep it from happening: if someone straps dynamite and nails to their midsection, you can probably keep them from boarding a plane, but you can't keep them from walking into the airport and exploding there before the security checkpoint, and they'll still accomplish precisely what they set out to do. It really isn't a problem you can solve by making more arrests or hitting the enemy harder (as evidenced by the situation with the IRA). It's most definitely not an Islamic thing by any means, and its often very easy to justify if you're the party committing it. It's hardly a very new observation to say that one man's terrorist is another man's freedom fighter. -- Captain Disdain (talk) 09:50, 20 August 2009 (UTC)

OK, I've checked out the link you gave -- it shows that there were actually about the same numbers (about 20 each) of major attacks by the Islamic terrorists as by the domestic terrorists (most of the latter either by left-wing radicals or by white supremacists); however, most of the terrorist attacks that happened in the last 40 years were, in fact, the work of Islamic terrorists, while many of the domestic terror attacks happened a long time ago (before WW2 for the most part). I'm not denying that domestic terrorism (especially the white-supremacist kind) is a serious concern, but right now Islamic terrorism is a much greater threat (especially since they got a worldwide network with a coherent agenda of waging jihad against the West, while the white supremacists are much less organized). As for "one man's terrorist is another man's freedom fighter", that's pure BS -- a terrorist is a terrorist is a terrorist, and ANYONE who says different is guilty of promoting terrorism! 98.234.126.251 (talk) 10:54, 20 August 2009 (UTC)

But like I said, it's not a complete list. It doesn't list every single act of terror, and it's also an example of systemic bias, which Wikipedia does suffer from: islamic acts of terror get a lot of press as terrorism, whereas man other actions do not. But the principle is the same. As for the freedom fighter thing, do you really think that the methods and goals of the French Resistance are fundamentally different from the roadside bombs you see in Iraq? Or that there's a huge moral difference between funding and arming al-Qaida, or funding and arming the Nicaraguans and Afghans (as the United States happily did back in the day)? The US didn't mind the terrorism these groups perpetrated at the time, because it was directed at people they considered enemies, even though the Contras in Nicaragua -- trained, funded and armed by the CIA -- kidnapped and raped civilians, among other things. Moral relativism is absolutely a major factor in how we view these things. And like I said, I'm not saying that islamic terror isn't a problem, because obviously it is. I'm just saying the issue isn't simple, and neither are the actual terrorists' motivations. It's not just that they're religious fanatics, just like Christian abortion clinic bombings aren't only motivated by Christian beliefs. (That said, people organizing these actions are certainly taking advantage of them -- using them to facilitate the actual acts of violence.) -- Captain Disdain (talk) 11:23, 20 August 2009 (UTC)

Thank you, Captain Disdain, for verbosely explaining the issue. My earlier objection might not have got the point across (and I admit I didn't really phrase it very well), but I hope we've managed to enlighten a few readers. Ricin is one of many scary things that are easily available and capable of large-scale harm; it is a worry to anyone who enjoys peace and security that such things exist. But the threats to public safety do not, categorically, come from a specific religious community - statistics do not even support that idea. Especially in the case of ricin, which was covered thoroughly in our article, the groups who have historically used this poison to spread fear are categorically not foreign terrorists. This does not mean foreign militants are non-existant, nor that they will never use ricin in the future - but without specific evidence, "idle speculation" is equivalent to racial profiling. Nimur (talk) 15:29, 20 August 2009 (UTC)

Excuse ME, Captain Disdain! Are you comparing the SAVAGES who attack our soldiers in Iraq to the FRENCH RESISTANCE?! Why, that's a completely IDIOTIC comparison -- for one thing, the French Resistance had a JUST CAUSE because they were DEFENDING A FREE NATION against the Nazis, whereas the Iraqi TERRORISTS are being motivated (and PAID, and SUPPLIED) by organizations whose goals are to CREATE AN ISLAMIC THEOCRACY EVERYWHERE THAT THEY CAN REACH, and to SNUFF OUT any democracy that they can! To compare one to the other is tantamount to saying that the Allies were no better than the Nazis because both sides used indiscriminate carpet-bombing of populated areas! You wouldn't make such a statement unless you were a Nazi, would you? 98.234.126.251 (talk) 00:46, 21 August 2009 (UTC)

Well, thanks for putting an end to this conversation. -- Captain Disdain (talk) 06:17, 21 August 2009 (UTC)

It's a fair point though (despite the shouting). Though one man's terrorist may be another's freedom fighter, ultimately there exists an external truth of the matter about which is which. 213.122.42.252 (talk) 01:00, 25 August 2009 (UTC)

And Nimur -- your statement that "the threats to public safety do not come from a specific religious community" is COMPLETELY counter-factual! For the record, I've been closely following terrorism news since the year 2001, and in that time there were THOUSANDS of terrorist attacks worldwide (both successful and otherwise) that were the work of Islamic terrorists, while the terrorist attacks by non-Islamics (IRA, KKK, Red Brigades, etc.) were comparatively few and far between. I really have to wonder where you get your news from, Nimur! 98.234.126.251 (talk) 03:03, 21 August 2009 (UTC)

Have you heard of the FBI? They're a fairly reliable source for crime statistics, and have actually got a whole web-site about their ricin investigations. [3] [4]. Nimur (talk) 06:22, 21 August 2009 (UTC)

I've just visited their website, and guess what they said at the top of their annual terrorism report: "The groups with the greatest capability to threaten are extremist Muslim groups." Draw your own conclusions, people! 98.234.126.251 (talk) 05:36, 22 August 2009 (UTC)

Doesn't say specifically with ricin though Nil Einne (talk) 20:47, 22 August 2009 (UTC)

I wasn't talking just about ricin, but about general propensity toward terrorist attacks; I was trying (quite successfully) to prove that islamic terrorists currently pose a much bigger threat to public safety than domestic terrorists. In case you haven't noticed, this discussion has gone from "terrorist attacks using ricin" to "terrorist attacks in general". So your statement that the islamics don't usually use ricin doesn't really prove or disprove my point, that the islamics are much more likely to carry out a terrorist attack than, say, the KKK. 98.234.126.251 (talk) 22:04, 22 August 2009 (UTC)

Guys, GUYS! This is a discussion about Extracting ricin from castor beans! If you want to go get side tracked and bullshit about terrorists and political crap, go find an apropriate forum for it, because this is not it. Ref Desk is NOT a chat forum and it is not a soap box. End of subject. Vespine (talk) 05:21, 21 August 2009 (UTC)

The original post was asking how difficult it is to obtain ricin. Pointing out which groups have historically been able to obtain ricin, and which groups have not, constitutes an on-topic response. That was my original goal. Sorry that we've been slightly sidetracked; sometimes it's hard to ignore blatant trolling. Nimur (talk) 06:11, 21 August 2009 (UTC)

Since when is a factually correct statement like "most terrorist attacks in recent years have been the work of Muslims" considered "blatant trolling"?! 98.234.126.251 (talk) 06:09, 22 August 2009 (UTC)

Emsley, J. (2008). Molecules of Murder: Criminal Molecules and Classic Cases. Royal Society of Chemistry. ISBN 978-0-85404-965-3. has a chapter about ricin. Nice book, good mix of science (not dumbed down but doesn't require advanced degree to understand) and culture/history. DMacks (talk) 06:47, 21 August 2009 (UTC)

haircuts

While brushing my palm over my gelled hair I noticed a very sharp sensation along my palm. There was however no blood. So now I'm curious -- are there any documented cases of hair cutting people, in a manner not unlike a paper cut? John Riemann Soong (talk) 19:35, 18 August 2009 (UTC)

Hair is essentially 1d while paper is essentially 2d. That added dimension can allow the paper to be both thin and stiff in certain situations. Hair would only be thin. With the aid of gel, perhaps it could be both thin and stiff enough to cause a cut, but I am not aware of it causing cuts. I don't think that the medical community has gone to the effort of documenting such an unusual way to get a very minor injury, but it is possible. Googlemeister (talk) 19:45, 18 August 2009 (UTC)

Pilonidal sinus typically occurs in the natal cleft. However hairdressers are known to develop this on the hands. Axl ¤ [Talk] 20:02, 18 August 2009 (UTC)

Yes, a barber I know told me she can get painfully poked by freshly cut hair, especially that of Oriental men, who have thicker hair follicles than most of the rest of us. A recently shaved head or buzz-cut can also present hairs that are standing upright, in prime poking position. So, if you give hair-cuts to Asian Marines, you'd best wear some thick gloves. StuRat (talk) 20:39, 18 August 2009 (UTC)

Plus as any man who hasn't shaved for a day or two (or for some poor folks if they shaved in the morning) will attest - their wife/partner's complaints of their face being "prickly" and "scratchy" have a point. Certainly my facial-hair feels scratchy enough to graze (if not cut someone). 194.221.133.226 (talk) 09:06, 19 August 2009 (UTC)

Hair can definitely cut you, or at least cut into you. Facial hair tends to be thicker and sturdier than the hair on your head (mine certainly is!), but even the latter can be surprisingly sharp under the right circumstances, soft as it is! Here comes the anecdotal evidence: I generally cut my own hair with a hair trimmer, which obviously results in a lot of short little hairs since I do it pretty regularly to keep it neat. I generally do this in the shower (though not during a shower, for reason which I hope to be obvious!), and I usually just scoop the hair up from the bottom with a damp piece of tissue. Of course, I don't quite get all of it, but a few stray hairs aren't going to clog up the drain the way a huge clump of them might. As a result, it's not unusual for me to encounter a surprisingly sharp pain in a toe a day or two later: there'll be a single, thin piece of hair sticking up from it. It's no big deal; once I pluck it out, the pain's gone, but I was pretty surprised to see how deep those things can go, and how sharp the sensation can be even though it's just a single, very thin piece of hair I've managed to step on. There's never been any blood I could see, but I wouldn't be surprised to find some one day. -- Captain Disdain (talk) 12:52, 19 August 2009 (UTC)

Locked in syndrome

Can a person with Locked-in syndrome obtain an erection?????? —Preceding unsigned comment added by 79.146.163.233 (talk) 19:58, 18 August 2009 (UTC)

I don't see why not. An erection is largely an autonomic response and does not require conscious muscle control. --Jayron32 20:46, 18 August 2009 (UTC)

This event is a climax (so to speak) in an extremely disturbing movie based on Dalton Trumbo's Johnny Got His Gun, made around 1970. alteripse (talk) 22:05, 20 August 2009 (UTC)

Additionally, a similar scene occurs in the John Irving novel The World According to Garp; in the event that leads to the conception of the title character. --Jayron32 02:25, 21 August 2009 (UTC)

What is "Real" Speed of Electricity?

Ever since i've learnt first time about electricity; i've imagined electricity having speed similar to light. Recently i've come into contact of an wikipedia article about speed of electricity which states that electrons in a conductor flow very slowly. But this information contradicts with some practical observations; which i'll state below. In case of Lightning electron travels from its source(few km above ground) to the ground at a flash; which gives hints how fast electrons are. Someone may argue in this case the flow of electron is not continious rather than a single splash. To convince them i'll present my second observation. Consider the case of a TV or computer monitor; these electronic components show picture by directing electron beam towards a photosensative plate. Here electrons emitted from negative terminal struck to positive terminal(photosensative plate) very fast. To continue this flow of electron the electrons must have to flow quickly inside conductor of positive & negative terminals otherwise the potential difference between them will continue to rise. So is there any satisfactory explaination of slow speed of electron through conductor(as claimed in wikipedia article)? —Preceding unsigned comment added by Shamiul (talk • contribs) 21:08, 18 August 2009 (UTC)

In a wire the actual electrical principle is transferred by spin alignment in nearby electrons (this is a gross simplification and I expect to be told off for saying it) - eg similar to how bar magnets in a row would align. Thus the electron does not need to travel at all for electrical power to be transmitted. Let me set your mind at rest on that issue. The second part about experimental determination of electron drift speed I cannot answer.83.100.250.79 (talk) 21:40, 18 August 2009 (UTC)

Also note that in a cathode ray tube the electrons travel in a vacuum - which is different from a wire - also in this case they must travel through the medium since they cannot transmit the electrical signal by influencing nearby electrons (there are no nearby electrons in CRT), this is different from the case in the wire.83.100.250.79 (talk) 21:44, 18 August 2009 (UTC)

(more) Also it's worth noting that in lightning or a CRT the field strength is very high eg 1000V per meter - classically the force on a charged particle is proportional to the field strength - thus in these cases the electrons would be expected to accerelate (and by extension move) very quickly. However in a wire (of low resistance) the field strength is very low eg 1V/m -so the electrons would be expected to move much more slowly from a classical perspecctive. 83.100.250.79 (talk) 22:18, 18 August 2009 (UTC)

The speed of electrical energy and the speed of electrons are two different things. Electrons can move at any speed from zero to the speed of light, more or less. In matter they tend to move with a slow average speed, because they keep bouncing off atoms, but in a vacuum like that inside a cathode ray tube, they can move at close to the speed of light. Electrical energy, on the other hand, is transmitted by photons, which move at the speed of light, because they are light.

How can we prove that electrons move slowly in matter? I don't know of a direct experiment to prove this, but it follows from mathematics. A current is a flow of electrons. One ampere equals one coulomb of charge per second. We know how many electrons it takes to make one coulomb, and we know how many electrons are in a given volume of matter (like a piece of wire), so we can calculate how fast the electrons must be moving to carry that coulomb past a given point in one second. This speed turns out to be very slow.

The reason that an electrical signal moves faster than electrons is that the signal is carried by photons, not by electrons. All the electrons along the entire current path (such as a long wire) start moving at almost the same time, because the electric field that makes them move is carried by photons. -Heron (talk) 21:49, 18 August 2009 (UTC)

I think what you are referring to is the drift speed of electrons. This is far less then the speed of light.66.133.202.209 (talk) 22:50, 18 August 2009 (UTC)

According to drift velocity: In a 1mm wire, with a current of three amps - the electrons are moving at about one meter per hour.

The way to understand how this works is to imagine a 20 foot long, 2" diameter pipe, completely full of ping pong balls. If you take another ball and paint it red and push it into one end of the pipe, another ball will pop out of the far end almost instantly. The speed of "pingpong-current" is very fast indeed - if the balls were stiff enough, it could even get close to the speed of light! However, if you continue to shove more balls into the pipe, it'll be many minutes before the red ball pops out of the far end. The speed of a pingpong ball in this system is really slow!

When you flip on a light switch, you start (very slowly) pushing electrons down one of the wires - electrons start popping out of the other end almost instantly - but the time for a particular electron to get from one end of the wire to the other is measured in hours to days!

SteveBaker (talk) 23:32, 18 August 2009 (UTC)

Or with AC electricity they don't move at all.Dacium (talk) 00:18, 19 August 2009 (UTC)

There is an article Drift velocity which shows how the drift velocity (if it exists) can be estimated. To my knowledge calculations of this type have a primary function of testing higher grade schoolchildren's ability to apply maths to physically abstract problems, and as such the 'drift velocity of an electron' is a common topic in school physics textbooks. However in my electrical experience I've never encountered a situation where this derived quantity was useful or necessary to the solution of a real world problem.

However it is still of interest - particularily in extension to the calculation of the movement of ions in a solution - such as when doing electroplating. In this case the net drift velocity can be correlated to the extent of electroplating - in fact the mass change over time on an electroplated substrate can be used to derive/calculate the average velocity of the ions.83.100.250.79 (talk) 23:36, 18 August 2009 (UTC)

The electrons move slowly, but the transfer of energy happens extremely quickly (near the speed of light). Imagine a pipe filled with water, if you put some water in one end, some water will pop out the other end straight away. You can imagine the same thing with electrons, an electron goes in one end and another one is instantly forced out the other end, the propogation of this force is near the speed of light.

In A CRT a high voltage field accelerates electrons from a very slow speed to a very high speed, and they are only able to travel at high speed because they are essentially in a vaccum and not in a metal. Just because they are travelling fast in one part of the circuit does not mean the electrons are not flowing in a closed circuit - they are still flowing, slowly in the metal, then fast in the air, the net amount leaving/returning at any point is still the same. Remember also that in AC electricity, the electrons don't 'flow' at all, they just sit there and vibrate. Its the electroncs fields pushing on each other that is 'electricity' not the electrons themselves. Lighting is similair but again different. No electron from the top of the strike is likely to end up at earth, each electron pushes on the next one below it, some will get free of atoms and be under such high voltage fields that they will breifely fly at very high speeds between atoms, even large numbers of atoms, all this combined causes the lighting strike in a cascade effect.

Also, If you apply a voltage to piece of metal at one end only, a tiny amount of electrons will be pulled from it, but metals have such a huge amount of electrons that it would take millions of volts to pull all the electrons from even a tiny peice of metal, this is why metals are such good conductors, because you can't pull all the electrons off the metal, so if you let the metal pull electrons into itself (by connecting the other end of the metal to the other voltage) you can easily make electrons flow, but they do so extremely slowly.Dacium (talk) 00:18, 19 August 2009 (UTC)

(restore comment removed by vandal 83.100.250.79) "Electricity" can flow much faster than the electron drift. The electrons in the power cord of an AC appliance may move back and forth very slowly and a short distance, 50 or 60 times per second, Lightning ionizes the atoms of the gasses in the air. The lightning impulse travels from earth to cloud or from cloud to earth faster than the individual electrons. A CRT does have an electron beam. The voltage gradient might be 30 kv over a fraction of a meter. Edison (talk) 04:23, 19 August 2009 (UTC)

Genome Studies

Is linkage analysis or genome-wide association studies one of the better and efficient approaches to identifying genome expressions or is there a better technique? —Preceding unsigned comment added by 71.143.156.160 (talk) 21:15, 18 August 2009 (UTC)

You might want to clarify what you mean by "genome expressions". If you are referring to the transcriptional "expression" of genes, neither of these techniques would be particularly helpful. Linkage analysis and genome-wide association studies are usually for making causal inferences between genes and specific phenotypes (for example: gene "X" is involved in the regulation of phenotype "Y") but they don't give information about how, when, and why a gene is transcribed. Instead you'd want to look into a cDNA microarray used for gene expression profiling, which can tell you the genes that are expressed in a given biological sample under a particular set of conditions. --- Medical geneticist (talk) 01:02, 19 August 2009 (UTC)

Species population

Is there a species whose population is similar to humans (6.7 billion)? I have been reading articles on world's most endangered species and it would be interesting to create a list comparing species by world population. --Kvasir (talk) 21:18, 18 August 2009 (UTC)

Well, German cockroach population is prob'ly in the trillions or even quadrillions. Same for many other insect species I'm sure (like ants, termites, houseflies, moskeeters, lice, aphids, etc., etc.) Note also that many of those species are harmful to humans (but that's a whole different topic). 98.234.126.251 (talk) 09:41, 19 August 2009 (UTC)

The closest I know is the chicken. Six for every human according to QI; our article says 24 billion six years ago; it's still not on the same order of magnitude either way. Vimescarrot (talk) 10:25, 19 August 2009 (UTC)

There are estimated 1.3 billion cattle, so that is also same order of magnitude (though off in the other direction) Googlemeister (talk) 13:20, 19 August 2009 (UTC)

I actually wrote a response to this question a few days ago but did not post it because, after re-reading it, I found that it didn't answer the question. All of the above responses similarly do not answer the question -- what does the German cockroach have to do with this question? The majority of insect populations are in gross excess of 6.7 billion. And to respond with organism populations that merely possess calculable order of magnitudes, how does that answer this question? DRosenbach ^{(Talk | Contribs)} 15:34, 19 August 2009 (UTC)

Well, if I can provide an answer in the same order of magnitude, and no-one can come up with a closer match, then as far as our ability to answer goes, I've won the "most similar" contest. On that basis the chicken and cattle answers seem to be entirely apropos. --Tagishsimon (talk) 15:38, 19 August 2009 (UTC)

Let's put it this way then. Of the estimated 1 million + animal species on this planet, it is likely that there is one or more with a population similar to that of humans (how similar is similar?). Locating an exact species that fits this criteria would be time consuming (if it is indeed possible) so myself & VC have provided familiar species that are within an order of magnitude. Googlemeister (talk) 15:44, 19 August 2009 (UTC)

Realistically - chickens and cattle 'bracket' the human population numbers quite nicely. For tiny animals like insects, the numbers are either insanely too large (eg ants, roaches) - or if the insects are rare or endangered, far too small. Probably there is some relatively obscure insect with the right population - but finding it would be impossible. We just don't keep track of insect populations that closely. For larger animals, it's likely that rats and mice have us way outnumbered - for most other large species, they're not going to come close to our numbers unless they are domesticated...and even if they might be comparable (maybe rabbits or something) - those kinds of populations can't possibly be counted - we have to estimate them, and the error in that estimation could easily be a factor of 5 or 10 - which would make them no better as examples than chickens and cose. Which brings us back to things like cats and dogs, pigs, chickens and cows that we could probably estimate fairly accurately...maybe to within a factor or two or three. There actually aren't many species that we have domesticated in enough numbers - so the answer is never going to be all that close - an order of magnitude is actually pretty good, all things considered. I'm certain that there is no closer candidate that we know with as much certainty. IMHO, our best possible answer is "Cows". SteveBaker (talk) 18:48, 19 August 2009 (UTC)

Thank you all for attempting to answer this very difficult question. I just thought someone might have already did a survey like this. I would imagine a species on the IUCN Least Concern list would be a good place to start if there are domesticated animals there. The list usually post estimated population as part of the assessment. I think the order of magnitude would be a good place to aim at. I agree, domesticated animals is a good place to start and the IUCN's assessment would be a good authoritative population estimate. Thanks. --Kvasir (talk) 21:40, 19 August 2009 (UTC)

Then of course you have to ask yourself if "population of individuals" is actually the relevant factor here, I would consider a million humans to be less "endangered" then a million ants, ignoring our obvious self centeredness. Putting it another way, if there were only 6.7 billion ants in the world, they would probably be quite rare. Another method perhaps more relevant for measuring species "success of propagation" is Biomass_(ecology). In which case, as it turns out, cattle also turns out to be a decent match to humans (156 to 100 millions of tons respectively) , a bit better then chickens anyway (15 to 100) . ( Vespine (talk) 23:38, 19 August 2009 (UTC)

Tundra Climates

Does tundra climates places the latitudes lies obetween 70 and 90 shade in blue on map get warmer than 60 deg F on summer times? The summer is only short only few months.--69.229.39.33 (talk) 21:20, 18 August 2009 (UTC)

Well, from what I know, Murmansk can get warmer than 15 C in the summer on occasion, but then it's got a warm current warming it up quite a bit. (It's hard to believe, but it's warmer in Murmansk beyond the Arctic Circle than in Arkangel further south on the White Sea.) FWIW 98.234.126.251 (talk) 09:32, 19 August 2009 (UTC)

Some arctic and antarctic regions can get remarkably warm in the brief summer. Even though the Sun may be at a low angle, you can still get sunlight 24 hours a day, if above the arctic circle or below the antarctic circle. The Gulf stream and similar currents can warm coastal areas, and, conversely, hot air blown up from the south over a continent can bring warm air that way. So, there are two trends in the tundra, it is colder, on average, but also the range of temps is wider than in the tropics. The result is that it gets much colder in winter there, but can sometimes get almost as warm as temperate regions in the summer. If we plot the temp range for temperate climates as asterisks (*) and the temp range for the tundra as dots (.), you can see that both are sinusoidal, but the magnitude is higher in the tundra and the average is lower:

  ^
  |      ***         ***
T |    *  .  *     *  .  *
E | **  .   .  ***  .   .  *** <- temperate zone
M |    .     .     .     .
P |  .          .           .  <- tundra
  |
  +---------------------------->
     W    S     W     S      W
             SEASON

StuRat (talk) 13:34, 20 August 2009 (UTC)

Longitude per mile

If one degree is away from Greenwich then how many miles is 1 E or W? For latitude 1 away from equator is 69 miles.--69.229.39.33 (talk) 22:44, 18 August 2009 (UTC)

Miles per degree longitude depends on what latitude you’re at. Roughly,

Miles per degree longitude = 69 cos(latitude)

Red Act (talk) 22:58, 18 August 2009 (UTC)

So if you're talking a position 1° east or west of Greenwich, London, England, that's at about latitude 51.48°, so the answer is that it's aobut 43 miles away. --Anonymous, 00:18 UTC, August 19, 2009.

Are miles per degree of latitude dependent on your latitude, or is that constant? Googlemeister (talk) 13:16, 19 August 2009 (UTC)

There's just a small variation, about 1% between poles and equator, due to the Earth not being spherical. See Latitude#Degree length. --Anonymous, 15:05 UTC, August 19, 2009.

Hence why on flat maps, they get severely distorted when near the poles. Googlemeister (talk) 18:46, 19 August 2009 (UTC)

Actually, no. The inaccuracies of various map projections have nothing to do with the latitude discrepancy; rather, they usually stem from longitude's properties. — Lomn 20:10, 19 August 2009 (UTC)

Yes, to compare with the 1% variation due to the Earth not being round, there is also a 100% variation due to your latitude. That is, you move something like 67 miles by going 1° east or west at the equator, and move no distance at all by going 1° east or west at either pole. StuRat (talk) 13:10, 20 August 2009 (UTC)

What I mean is that while you only have a 1% change in the latitude scale over the 0-90 deg range, your longitude changes from 69 miles all the way down to 0, so when you get near the poles, you are getting distortions of 20 to 1 or even greater. Googlemeister (talk) 13:26, 20 August 2009 (UTC)

plate tectonics

Do all the plates move in same exact speed or some plates moves in a slower or faster speed? Do small plates moves faster or bigger plates moves faster.--69.229.39.33 (talk) 22:45, 18 August 2009 (UTC)

I don't think the plates all move at the exact same speed, but there are prob'ly many other factors besides size. FWiW 98.234.126.251 (talk) 22:50, 18 August 2009 (UTC)

That's wierd I thought I posted a reply to this question. Anyway according to this linkthey aren't. There are some tables down below. Remember the whole point of plate tectonics is that the plates are fractured and seperate so naturally they should move at different speeds (I'm assuming from the differential heating and cooling and the forces other plates exert on them (along plate boundaries)66.133.202.209 (talk) 23:41, 18 August 2009 (UTC)

The plates move at very different speeds. Plates attached to subducting slabs (subucting tectonic plates) typically move much faster than those surrounded by passive margins (like around the Mid-Atlantic Ridge). Where there is a slab, it is like holding a rug partway off a table: the weight of the portion of the rug off the table works to pull the rest of the rug forwards and off of the table. Where there isn't a slab, this very strong driving force is not available and the plates move more slowly. 66.133.202.209 above is partially right, but the guess isn't quite right. Interactions along plate boundaries are important, but much of plate motion comes from their coupling with the mantle.

Also, in representations of tectonic plate motions, some point must be set as the reference, so all velocities will be relative to that plate's velocity. But that's more of a data referencing issue than a science issue. Awickert (talk) 20:19, 19 August 2009 (UTC)